Okay, going back to your previous statement, your tap has high ammonia? THIS is your problem. :) It's not good, but it can be managed. At least now you know what the problem is. :)
With this, you have three options.
You can cycle the tank.
You can heavily plant the tank with live plants (this will cycle it just because the plants use the ammonia)
You can purchase filtered or reverse osmosis water.
The Prime isn't actually fixing your high tap ammonia. Prime ONLY neutralizes the ammonia for a *day or two*, after that, the ammonia is back at full strength unless it's being used by lots of plants, or by the BB's in a cycled tank. So, even when you're doing water changes, you're just adding in more ammonia, even with the Prime. This is why your guy is having problems, all the water you're changing, thinking that you're making him healthy, is really only hurting him. Of course, NOT changing the water though is just as bad. It's a no-win situation. :(
As you said you were unable to cycle (I understand, it can be hard, please don't think I'm fussing at you :) ) and I'm assuming that lots of live plants are out? (they can be expensive) Then your other option is to buy filtered water, or if you have a filter at home you can filter it yourself. The at-home options are like a Brita water filter pitcher or a Brita filter that goes on the end of your tap in the kitchen, or even if you have filtered water in the door of your fridge. It's too cold straight from there, but you can heat it up before adding it to your tank and you'll be good. The filtered water isn't the best option, but it's better than the high ammonia your tank is going to have all the time because of the ammonia in your tap. (The filtered water isn't going to have the nutrients that your fish needs, so make sure you feed good quality NLS pellets and you may also need to get some fish vitamin supplements as well, but it's FAR better than killing your boy with the high ammonia.)
If you can't filter the water at home, at most grocery stores and walmart you can get those big 5gallon jugs of water, these are filtered reverse osmosis water, and will be safe for your fish. That's probably your best option.
I really don't think that the AQ salt is going to do anything because of your ammonia being high. It's like putting Neosporin on a burn and then just sticking your hand back into the boiling water again. The Neosporin can't work because the initial irritant is still there and causing more damage.
I'm so sorry that you're having these issues, but hopefully this will help. :) Once your boy is in ammonia-free water, he'll start to heal on his own. :)